This invention relates to the field of fiber optics and, more particularly, to the storage and organization of fiber optic splices and associated slack.
Optical fiber communications systems are used extensively in the telecommunications industry because of their large information carrying capacity, their virtually noise-free performance, and the long span distances achievable with optical fibers before regeneration and amplification of the signal is required. Practical limits on the lengths of optical fiber cables that can be manufactured and installed typically require that many splice points be included over the total cable route.
At each splice location, the optical fibers are separated from the other protective cable components for splicing and are, thus, more susceptible to damage. In addition, the optical fibers at a splice point are handled by a technician who must splice the fibers and then store the splice and associated slack in a protective enclosure.
Although an optical fiber cable can carry signals over relatively long distances without requiring repeaters, one common architecture includes one or more drop locations along a main cable route. In other words, it may be desirable to connect certain fibers to drop cables along the main cable route. Each such drop or splice point requires the protection of the cable ends and individual splices. More particularly, a splice closure is typically provided for terminating the cables and storing the splices.
Accordingly, enclosures for protecting optical fiber splices have been developed and are readily available. Typically, these enclosures include one or more splice organizers, or splice trays as they are also called, on which the individual splices and associated slack are mounted. For example, the assignee of the present invention manufacturers a conventional splice enclosure and splice organizer under the model designation FOSC 100. Siecor Corporation of Hickory, N.C. makes splice enclosures under the model designations SC2 and SC4-6.
U.S. Pat. No. 4,679,896 to Krafcik, for example, discloses a butt splice closure where the ends of two cables to be spliced together are routed through one end plate of a generally cylindrical housing. The housing is provided by a pair of generally circular end plates, and a tubular cover connecting the two end plates. Raychem, the assignee of the present invention, also manufactures butt splice closures wherein the cables to be spliced are brought in from a single end of the housing. A series of pivotally mounted splice organizers are provided. The pivotally connected splice organizers permit organizers to be moved to a raised position to facilitate access to an underlying organizer. A fixed slack basket may be positioned under the splice organizers to store slack buffer tubes, for example. An example includes U.S. Pat. No. 5,323,480 to Mullaney et al., the disclosure which is hereby incorporated by reference in its entirety, assigned to the present assignee, the disclosure which is hereby incorporated by reference in its entirety.
Another general type of splice closure is the in-line closure wherein cables enter the overall housing from opposing ends. An in-line splice closure may be particularly desirable for a drop or branch cable location where the main cable includes a significant number of fibers that can pass through the closure without requiring splicing. Only those fibers that need to be dropped are spliced and the remaining fibers can be stored within the housing.
For example, U.S. Pat. No. 4,805,979 to Bossard et al. discloses such an in-line fiber optic splice closure. The closure includes two mating shell portions which are secured together to define an overall protective housing. Cable entry ports are provided at each end of the housing and are defined by arcuate wall portions between the base and cover housing portions. A slack storage area is defined in the base by a pair of inwardly extending retaining brackets connected at a medial portion of the base. The cable ends are terminated adjacent the cable ports. A series of splice organizers are connected to the base above the slack storage area. Each splice organizer stores a number of individual fiber splices.
A splice organizer is typically limited in the amount of space it may occupy although it must permit the mounting of the individual splices and permit storage of the slack optical fibers in a relatively neat configuration. To hold a sufficient amount of slack to permit splicing, a splice organizer typically accommodates one or more bends of slack optical fiber in slack loops that cannot be sharply bent and thereby exceed the minimum bend radius for the optical fiber. Exceeding the bend radius causes microbending losses, that is, increased attenuation of the optical signal. In addition, the optical fibers may be physically damaged by exceeding the minimum bend radius. An approach to storing a sufficient length of slack is to use multiple loops for each individual fiber. See, for example, U.S. Pat. No. 4,373,776 to Purdy and U.S. Pat. No. 4,765,709 to Suillerot et al.
The slack loops of conventional splice organizers are frequently permanently entangled with each other as part of the normal course of splicing and routing of the slack for storage on the splice organizer. Unfortunately, it is very difficult to access an individual splice after all of the splices have been completed because of the entangling of the slack optical fibers. In almost all fiber optic communications systems, it is critical that high quality and high reliability splices be obtained. Fusion and mechanical splicing techniques and equipment have been developed that permit low loss, high quality, and durable splices to be obtained. However, it may sometimes be necessary to remake or repair splices to achieve the desired splice quality. The inability to readily reaccess a splice, such as to remake the splice, is a significant shortcoming of conventional fiber optic splice organizers.
Fiber cables are also available of a ribbon type, such as manufactured by ATandT, wherein several optical fibers are arranged in side-by-side relation and secured together by an adhesive layer. However, another difficulty with conventional splice organizers and techniques is that organizers for ribbon-type fiber optic cables require that every fiber in a given ribbon be spliced to every correspondingly positioned fiber of another fiber optic ribbon. Thus, any flexibility in interconnecting a predetermined individual optical fiber to an optical fiber in a different position or on a different ribbon is simply not available. Moreover, should it be necessary to repair only a single optical fiber splice of the ribbon, all of the splices must then be broken and remade. Thus, unnecessary communications systems downtime is experienced because of the need to work with all of the fibers in the ribbon, rather than being able to efficiently access only one optical fiber from the ribbon.
In many new fiber optic communications applications, such as in campus-type networks or cable TV networks, high fiber counts and a large number of drop points are required. Unfortunately, since conventional fiber optic organizers cannot accommodate splices between individual optical fibers when ribbon cables are used, interconnection flexibility for such a system is severely limited.
U.S. Pat. No. 5,278,933 to Huntsinger et al., issued Jan. 11, 1994, the disclosure which is hereby incorporated by reference in its entirety, provides a splice organizer and method for securing optical fiber splices and slack of the cables, which also permits ready separation of the optical fibers even after all the splicing has been completed, such as to facilitate remaking the splice. It also allows break out and splicing of individual optical fibers in the ribbons to enhance interconnection flexibility and permit the repair of individual optical fibers from an optical fiber ribbon.
In this structure, the fiber optic splice organizer includes a generally rectangular base. A splice securing structure is positioned on a medial portion of the base between the first and second sides and adjacent the first end of the base for securing a plurality of optical fiber splices on the base. A slack guide structure is positioned on the base for guiding slack portions of laterally spaced apart first and second optical fiber groups from the first end of the base and along respective portions of the base adjacent the first and second sides. The slack guide structure guides the slack into a plurality of respective first and second slack loops overlying each other adjacent the second end of the base and back to the splice securing structure from respective first and second sides of the base so that the overlying respective slack groups of the first and second optical fiber groups are readily separable from each other.
U.S. Pat. No. 5,802,237 to Pulido, issued Sep. 1, 1998, discloses an optical fiber organizer having first and second levels formed as elliptical structures where both mechanical and fusion splice devices are held on each level. Each level also includes a first fiber port and a second fiber port. Thus, splices and entry of fiber occurs on both levels. However, it would be advantageous if slack storage was separate from splicing and initial guiding of fiber and any splice storage allowed the separation of one side of the splice from the other. Also other structures as disclosed above typically have a separate splice tray and slack storage tray, thus making it difficult to organize and identify fibers and ribbons.
It is therefore an object of the present invention to provide a fiber optic splice organizer where the optical splices and slack are separate but on one organizer and entry points for the fibers and the slack area are separate from the splice area.
The present invention now allows adequate separation of the splices on a different structure from the slack, and permits the slack storage to be removed, while still having the separation from one side to the other. The invention allows one to splice on one level (upper) of the tray and store splice slack as well as uncut fiber storage on another level. This allows separation of the splices and slack storage on the same organizer as well as separating ribbon or fiber groups from other ribbon or fiber groups in the same closure. The splice storage allows one to separate one side of the splice from the other. This capability is significant for resplicing live working fibers. The organizer allows one to separate and break out a ribbon fiber to splice a single fiber. The organizer allows one to easily splice and store fibers/ribbons on the same organizer. It gives a good separation between the splices and fiber storage. Other organizer systems have separate splice trays and slack storage trays. This makes it difficult to organize and identify fibers/ribbons. Separate groups of fibers/ribbons can be spliced and stored on the same splice organizer. The organizer is compatible with both in-line and butt joints. Additionally, the slack can be placed in an area separate from the splice connections to allow one to work on the splice connections without interference from any slack cable or ribbon.
In accordance with the present invention, a fiber optic splice organizer secures a plurality of optical fiber splices between first and second optical fiber groups and secures the slack associated therewith. A generally longitudinally extending lower base member has lengthwise extending first and second opposing sides and widthwise extending first and second opposing ends on which slack optical fibers can be stored in looped configuration. Naturally, the optical fibers in the following description can refer to ribbons.
A hinge is connected at one end and adapted to pivotally mount the base member to the housing. Means is positioned at the end of the base member to be pivotably mounted for receiving optical fibers. An upper splicing tray is positioned on the lower base member and at least one splice holder is positioned on the upper splicing tray for securing a plurality of fiber optic splices in side-by-side relation. The slack is then placed under the upper splicing tray within the area formed between the upper splicing tray and the lower base member.
In one aspect of the present invention, the fiber optic splice organizer includes a guide for receiving and guiding optical fibers. The guide could include an arcuate member that allows the optical fibers to extend arcuately around the interior lower base member adjacent a pair of opposing side walls extending upwardly from the lower base member, such that the walls retain slack portions of optical fibers adjacent thereto.
Guide tabs extend from the sidewalls to aid in retaining slack portions of optical fibers within the lower base member. The upper splicing tray can include a locking member that permits the upper splicing tray to snap fit onto the lower base member. The upper splicing tray is typically substantially rectangular configured and is secured to the lower base member at the end opposite the pivotal mount. The upper splicing tray can also be secured to the lower base member at a medial portion of the lower base member. The splice holders can also be adapted for splicing ribbon fiber optical fiber and can be adapted for in-line splicing and butt splicing.
In still another aspect of the present invention, a fiber optic splice closure of the present invention includes a housing and means positioned on the housing for securing one or more fiber optic cables to the housing. A plurality of fiber optic splice organizers secure a plurality of optical fiber splices between first and second optical fiber groups and secures the slack associated therewith. The fiber optic splice organizers are positioned within the housing and have an end pivotally connected to the housing and moveable between a stacked position and a raised position to facilitate access to the underlying area of the organizer, such as where other stacked fiber optic splice organizers are positioned.
Each fiber optic splice organizer further comprises a generally longitudinally extending lower base member that has lengthwise extending first and second opposing sides and widthwise extending first and second opposing ends in which slack optical fibers can be stored in looped configuration. A hinge is connected at one end that pivotally connects the base member to the housing. Means is positioned at the pivotally connected end of the base member for receiving optical fibers. An upper splicing tray is positioned on the lower base member. At least one splice holder is positioned on the upper splicing tray for securing a plurality of fiber optic splices in side-by-side relation. The housing is generally cylindrically configured and cable termination means can be connected to the housing for securing one or more fiber optic cables thereto.
In a method aspect of the present invention, the method organizes a plurality of optical fiber splices between first and second optical fiber groups and the slack associated therewith. A lower base member having lengthwise extending first and second opposing sides is provided. It also has opposing sidewalls extending upwardly from the base, and widthwise extending first and second opposing ends. The method comprises the step of securing optical fiber splices that exist between first and second optical fiber groups on splice holders that are positioned on a medial portion of an upper splicing tray, which is secured to the lower base member. The method also comprises the step of coiling the slack optical fibers, inserting a portion of the coiled slack optical fibers under the upper splicing tray, and guiding the slack optical fibers that have not been inserted under the upper splicing tray along respective portions of the lower base member adjacent the upwardly extending walls of the first and second sides.
In still another method aspect of the present invention, the method comprises the step of securing the slack optical fibers under guide tabs that extend from the sidewalls across a portion of the lower base member. The method also comprises the step of coiling the slack optical fibers into a figure eight loop. The method also comprises the step of mounting the splice holder adjacent the first end of the lower base member and securing the first and second optical fiber groups in laterally spaced apart relation on the lower base member adjacent the first end of the lower base member prior to splicing.